The present invention relates to industrial process control and monitoring systems. More specifically, the present invention relates to diagnostics used in such systems.
Industrial process control and monitoring systems are used to monitor or control many types of industrial processes. For example, monitoring systems can be used to monitor the transfer of process fluids, such as oil, gasoline, etc., while industrial process control systems are used to control industrial processes. For example, a process transmitter such as a pressure transmitter can be configured to sense a process pressure and transmit information related to the sensed pressure to a remote location, such as a control room, over a two wire process control loop. The two wire process control loop is one example communication standard used in such systems. In a control system, in response to a sensed process variable (i.e., pressure), a controller can be configured to change operation of the process as desired such as, for example, controlling the position of a valve.
If a process device (a process variable transmitter or a process controller) fails or is otherwise not operating within its specifications, the process being controlled can be disrupted as well as the process control equipment. Various techniques have been used to identify or “diagnose” the condition of operation of the process. Such techniques can be used to provide an indication that a component has failed so that the process can be shut down and service personnel can replace the component. Additionally, in some configurations, the diagnostic techniques attempt to identify a failing component prior to that components ultimate failure thereby allowing preventive maintenance to be performed.
Some techniques used to diagnose process control and monitoring systems utilize process noise. Process noise is the higher frequency variation of pressure signal due to equipment and general fluid flow. One process noise example might be the high frequency pressure variation generated by flow through an orifice plate, or a turbine pump. The process noise can be monitored and used to identify a failing or failed component in the process control and monitoring system. Such techniques are described, for example, in U.S. Pat. No. 6,601,005 entitled “PROCESS DEVICE DIAGNOSTICS USING PROCESS VARIABLE SENSOR SIGNAL”, issued Jul. 29, 2003, and assigned to Rosemount Inc.